Am 09.06.22 um 17:19 schrieb Felix Kuehling:
Am 2022-06-09 um 10:21 schrieb Michal Hocko:
On Thu 09-06-22 16:10:33, Christian König wrote:
Am 09.06.22 um 14:57 schrieb Michal Hocko:
On Thu 09-06-22 14:16:56, Christian König wrote:
Am 09.06.22 um 11:18 schrieb Michal Hocko:
On Tue 31-05-22 11:59:57, Christian König wrote:
This gives the OOM killer an additional hint which processes are
referencing shmem files with potentially no other accounting for
them.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
mm/shmem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/shmem.c b/mm/shmem.c
index 4b2fea33158e..a4ad92a16968 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2179,6 +2179,11 @@ unsigned long
shmem_get_unmapped_area(struct file *file,
return inflated_addr;
}
+static long shmem_oom_badness(struct file *file)
+{
+ return i_size_read(file_inode(file)) >> PAGE_SHIFT;
+}
This doesn't really represent the in memory size of the file,
does it?
Well the file could be partially or fully swapped out as anonymous
memory or
the address space only sparse populated, but even then just using
the file
size as OOM badness sounded like the most straightforward approach
to me.
It covers hole as well, right?
Yes, exactly.
So let's say I have a huge sparse shmem file. I will get killed because
the oom_badness of such a file would be large as well...
Would killing processes free shmem files, though? Aren't those
persistent anyway? In that case, shmem files should not contribute to
oom_badness at all.
At least for the memfd_create() case they do, yes.
Those files were never part of any filesystem in the first place, so by
killing all the process referencing them you can indeed free the memory
locked by them.
Regards,
Christian.
I guess a special case would be files that were removed from the
filesystem but are still open in some processes.
Regards,
Felix
What could happen is that the file is also mmaped and we double
account.
Also the memcg oom handling could be considerably skewed if the
file was
shared between more memcgs.
Yes, and that's one of the reasons why I didn't touched the memcg
by this
and only affected the classic OOM killer.
oom_badness is for all oom handlers, including memcg. Maybe I have
misread an earlier patch but I do not see anything specific to global
oom handling.
As far as I can see the oom_badness() function is only used in
oom_kill.c and in procfs to return the oom score. Did I missed
something?
oom_kill.c implements most of the oom killer functionality. Memcg oom
killing is a part of that. Have a look at select_bad_process.
